February 14, 2011 - PASADENA, Calif. -- Just one year before its Feb. 14 encounter with comet Tempel 1, NASA's Stardust spacecraft performed the largest rocket burn of its extended life. With the spacecraft on the opposite side of the solar system and beyond the orbit of Mars, the comet hunter's rockets fired for 22 minutes and 53 seconds, changing the spacecraft's speed by 24 meters per second (54 mph). The burn was a result of an international effort to determine something that could very well be indeterminate -- which face of Tempel 1 will be facing the sun when Stardust hurtles by tonight, Feb. 14, the evening of Valentine's Day in the United States.

"Our goal is to re-visit a comet to look for changes that occurred since NASA's Deep Impact mission took a look five-and-a-half years ago," said Tim Larson, Stardust-NExT project manager from NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We may also see the crater that Deep Impact created in 2005, but because of Tempel 1's rotation, there is no guarantee. At the end of the day, whatever we see there should provide some great new science."

While comets have been observed and postulated on for centuries, cometary science acquired literally "on the fly" is a relatively new field. Since 1984, there have been spacecraft flybys of six comets. Of these, none involved the ability to look for changes that may have occurred as a result of the comet's orbit around the sun. That is, until Stardust-NExT and Tempel 1 meet tonight.

"You could argue that comet Tempel 1 is the most unique icy dirtball in our solar system," said Joe Veverka, Stardust-NExT principal investigator from Cornell University, Ithaca, N.Y. "Not only does it have many intriguing physical characteristics that fascinate the scientific community, it also has been analyzed and scrutinized time and again from the ground and space."